One means here by “LTE access network” the E-UTRAN (“Evolved Universal Terrestrial Radio Access Network”), which is an evolution of the UMTS (“Universal Mobile Telecommunications System”) radio access network towards a high data rate, low latency and packet optimized radio access network, currently specified by the 3GPP (“3rd Generation Partnership Project”), notably in 3GPP Technical Specification 36.300. As described in this Technical Specification 36.300, the E-UTRAN comprises base stations called eNBs (“evolved Node Bs” or “E-UTRAN Node Bs”). In the control plane, each eNB comprises a S1 interface which is connected to one or several Mobility Management Entities (or MMEs) that belong to a core network called EPC (“Evolved Packet Core”). An eNB is connected to all the MMEs controlling the pool area(s) it serves. A MME is connected to all the eNBs serving a pool area controlled by a MME pool it belongs to. Moreover in a pool area one MME may be designated as master.
As it is known by the man skilled in the art, it has been proposed to introduce a new function related to SON (“Self-Optimizing Networks”) in LTE access networks. This new function is called ANRF (“Automatic Neighbour Relation Function”). It applies when a User Equipment (or UE) informs the eNB to which it is connected, that it has detected a new neighbouring cell. It is recalled that an eNB controls at least one cell (associated to a cell identifier (called “global cell identifier”)), that each eNB belongs to at least one tracking area identified by a code called TAC (“Tracking Area Code”, which is generally a part of a tracking area identifier) and that eNBs may be connected therebetween through X2 connections.
According to ANRF, upon detection and reporting of a new neighbouring cell to a serving eNB, this eNB can ask a user equipment (or UE) to further read, decode and report what is the global cell id of this new neighbouring cell. When this eNB receives the global cell id, it has to derive from the global cell id at least one transport layer address (or TLA) that will enable it to try to dynamically setup an X2 connection with the eNB that controls the corresponding new detected cell.
In order to derive a transport layer address (or TLA) from a global cell id, an eNB must access either a central server of the DNS (“Domain Name Server”) type or a local database that is supposed to have been previously populated by an O&M configuration (which is known to be dull and subject to errors). So, the current ANRF function is not fully automated.
At least two proposals have been made to automate the retrieval of the transport layer addresses.
A first proposal consists in constructing standardized Fully Qualified Domain Names (or FQDN) based on global cell ids in order to resolve the IP addresses by a standardized DNS look-up. However, this proposal has not been retained by 3GPP so far because it puts too much constraint on the global cell ids. Indeed, it requires definition of standardized cross-domain FQDN and associated building rules.
A second proposal consists of using classical vendor DNS look-ups but requires coordination effort to populate and coordinate inter-vendor DNSs and proprietary look-up implementations in order to be able to look-up a global cell id that is unknown in an initial node domain.
Moreover, establishment of X2 connections only based on global cell ids may induce security problems.